An Actin promoter drives expression of a Drice-based sensor (DBS) of initiator caspase activity. The sensor is a fusion protein composed of Tag:M(mCd8a) transmembrane domains, a mutated form of Drice that carries a C211A mutation in the catalytic site (rendering it inactive) and that is truncated such that only 16 amino acid residues remain after the the initiator caspase cleavage site TETD/G, and the QF driver. In the absence of caspase activation the fusion protein is tethered to the cellular membranes outside the nucleus (due to the Tag:M(mCd8a) tag). In the presence of an initiator caspase, the Drice sequence can be cleaved at the TETD/G site, releasing the QF driver and allowing its translocation to the nucleus, where it can activate a QUAS-driven responder transgene.